Method of depositing gelatin



United States Patent 3,502,558 METHOD OF DEPOSITING GELATIN Harvey A. Hodes, Eatontown, N.J., assignor to the United States of America as represented by the Secretary of the Army No Drawing. Filed Nov. 3, 1967, Ser. No. 681,064 Int. Cl. B01k 5/02; C23f 13/00 U.S. Cl. 204-181 6 Claims ABSTRACT OF THE DISCLOSURE Gelatin is deposited on a cathode from an aqueous colloidal dispersion of gelatin by adding a water soluble inorganic salt of silver, nickel, or cobalt to an aqueous colloidal dispersion of gelatin provided with a suitable anode and cathode, and then applying an EMF across the electrodes.

The invention described herein may be manufactured, used, and licensed by or for the Government for governmental purposes without the payment to me of any royalty thereon.

BACKGROUND OF THE INVENTION This invention relates in general to a method of depositing gelatin and, in particular, to a method of depositing gelatin on a cathode.

It has been known that gelatin, either by itself, or in the presence of common electrolytes, always migrates to and is deposited on the anode of an electrolytic cell under an applied EMF. This is not always desirable where one wishes to reverse the conventional anodic deposition of gelatin, and thus deposit gelatin on the cathode.

The general object of this invention is to provide a method of depositing gelatin on a cathode.

A more specific object of this invention is to provide such a method as will be suitable in an electrophotopolymerization procedure, wherein the polymer image formed on the cathode will be enhanced by the accompanying deposition of gelatin.

SUMMARY OF THE INVENTION Gelatin is deposited on a cathode by preparing an aqueous colloidal dispersion of gelatin, providing the dispersion with a suitable anode and cathode, adding a salt of either cobalt, nickel, or silver to the dispersion, and applying an EMF across the electrodes.

The aqueous colloidal dispersion may contain other electrolytes, as, for example, sodium chloride, sodium citrate, or in general water soluble metal salts of common anions. The gelatin is present in the colloidal dispersion in an amount ranging from about 1 percent to about 20 percent by weight of the dispersion.

The salts that can be added to the colloidal dispersion are preferably water soluble, inorganic salts of silver, nickel and cobalt. Particularly desirable salts are silver nitrate, nickelous chloride, and cobaltous chloride. Salts of silver, nickel, or cobalt can be used alone or in combination. The amount of salt(s) used is about 1 to 10 percent by weight of the gelatin in the dispersion.

Any electrically conductive material may be used as either the cathode or the anode in the deposition. Thus,

electrically conductive metals such as iron, stainless steel, copper, gold or platinum are suitable electrode materials. Evan an electrically conductive carbonaceous material such as graphite can be used as the electrode.

The EMF that is applied to the dispersion can vary from 3 volts to 250 volts, depending on the concentration of gelatin, and concentration of electrolytes present. The pH range in which this process operates most efficiently is from about pH 4.0 to about pH 11.0, depending on the 3,502,558 Patented Mar. 24, 1970 concentration and type of gelatin and concentration of electrolyte present.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An aqueous dispersion of gelatin is prepared containing 10 grams of gelatin per grams of water. To this is added 1.0 gram of nickelous chloride. 0.01 gram of sodium citrate is then added to the mixture. The resulting pH of the dispersion falls between 5 and 6.5.

Into the above dispersion are placed two steel electrodes, separated by about 1 cm. A voltage of 22.5 volts is applied across the electrodes for 3 seconds, and the electrolysis is stopped. A skin of gelatin is observed at the cathode. The electrolysis is also initiated at lower or higher voltages, with a corresponding increase or decrease in the time of voltage applied.

Thus, it is now found that it is possible to reverse the electrodeposition of gelatin. A practical application of the invention is in a photoelectric imaging device in which polymer formation occurs at the cathode. Such devices are disclosed and claimed in US. patent applications of Hodes and Zerner, Ser. No. 670,815 and Ser. No. 670,816 filed Sept. 26, 1967, and assigned to the same assignee. If a photoconductive layer is substituted for one electrode, and a conducting metallic substrate containing the necessary ingredients, including gelatin and a polymerizable monomer for electro-polymerization, is made the other, a practical utility of the embodiment becomes clearer.

If the polymerization reaction occurs at the cathode, the depth and density of the image is enhanced by the accompanying insolubility of the gelatin. This is, in efiect, an added stage of amplification.

The foregoing description is to be considered merely as illustrative of the invention and not in limitation thereof.

What is claimed is:

1. A method of electro-depositing gelatin from an aqueous colloidal dispersion of gelatin, comprising adding a water soluble, inorganic salt of at least one member of the group consisting of cobalt, nickel, and silver to an aqueous colloidal dispersion of gelatin provided with a suitable anode and cathode, and applying an EMF across the electrodes whereby the gelatin deposits on the cathode.

2. A method according to claim 1 wherein the water soluble inorganic salt is at least one member of the group consisting of silver nitrate, nickelous chloride, and cobaltous chloride.

3. A method according to claim 1 wherein the water soluble inorganic salt is a nickelous chloride.

4. A method according to claim 1 wherein the anode is an electrically conductive material selected from the group consisting of iron, stainless steel, copper, gold, platinum, and graphite.

5. A method according to claim 1 wherein the cathode is an electrically conductive material selected from the group consisting of iron, stainless steel, copper, gold, platinum, and graphite.

6. A method according to claim 1 wherein the gelatin is present in the aqueous colloidal dispersion in an amount ranging from about 1 percent to about 20 percent by weight of the dispersion and the water soluble inorganic salt selected from at least one member of the group consisting of cobalt, nickel, and silver is present in an amount of about 1 to 10 percent by weight of the gelatin in the dispersion.

References Cited FOREIGN PATENTS 518,554 2/1940 Great Britain. I

HOWARD S. WILLIAMS, Primary Examiner 

